Liquid crystal display devices are used across a wide range of industries and, taking advantage of their thinness, low power consumption, etc., are increasingly applied to mobile terminals (portable devices) such as cell-phones and tablet PCs.
Backlights used in liquid crystal display devices consist of a light source, a light guide plate, and an optical sheet, which are generally held integrally by a resin molded frame. Convex protrusions are then provided at several points on the peripheries of the optical sheet and the light guide plate in a manner fittable into concave fitted portions provided in the frame to prevent the optical sheet and the light guide plate from being displaced when an external force is applied thereto.